"I hope there's words that will just echo and resonate, and say, "yes, there is empathy, there is humanity, there is hope for the world", because I think this service is the platform that can really start to change humanity depending on the right words and - it's a church, people of god - how they convey the message to mankind".
It also addressed the anger of many survivors over what they perceive as the neglect of their community before and after the fire.
Jeremy Corbyn, the Labour leader, hugged survivors outside the cathedral but some said they had not even realised that the prime minister had been there.
Ben Gabbitas, whose close friend Sheila died in the fire, hailed the Royals' presence as a constant strand of support through the uncertainty of the past six months.
People gather on the steps after a Grenfell Tower National Memorial Service.
Clarrie Mendy, whose cousin Mary Mendy and her daughter Khadija died in the fire, has been helping shape the multi-faith service, which will focus on remembering the 71 victims of the June 14 tower block blaze.
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Senate Minority Leader Chuck Schumer (D-New York) reacted Friday by saying, "God bless wealthy people". Republicans are confident future Congresses will extend the cuts, but there is no guarantee of that.
Maureen Smith, the mother of his long-term partner, said Mr Bernard had opened his door to families who had fled up the tower in a desperate attempt to escape the flames. Still she cries, every day, every second when we are talking about our father, all the memories come out again. The official death toll stands at 71.
Later, a young Syrian musician played a mournful tune on the oud, an instrument commonly played in the Middle East and parts of Africa, where many Grenfell residents had ties.
As the ceremony began, A Green For Grenfell banner adorned with a heart was carried in as a hymn was sung, before the Very Reverend Dr David Ison, Dean of St Paul's, welcomed the congregation.
Ms Campbell defended the council, saying it was doing everything it could to secure quality homes for affected families, but members of the Grenfell community complained of a slow, confusing process.